Fiber-optic communication is a method of transmitting voice, video, data or other information by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information. In most cases, fiber-optic communication involves at least three components, a transmitter that emits light (e.g. light-emitting diodes and laser diodes), a fiber-optic cable that carries the light to another location, and a receiver that converts the light into electrical signals.
Fiber optic cables typically comprise a core, a cladding, and a buffer (a protective outer coating), in which the cladding guides the light along the core using the physical principle of total internal reflection. The core of the fiber-optic cable is made of a material, such as high quality silica or plastic, which has a higher refractive index than the cladding. Consequently, light rays which enter the fiber-optic cable at an angle below the critical angle reflect off the cladding and are guided down the cable. However, light rays which enter at above the critical angle partially reflect and partially refract each time the light ray encounters a boundary between the core and the cladding. As result, the light's intensity, and thus the signal carried by the light, becomes attenuated and is eventually lost.